The present invention relates to a refrigerating machine such as a refrigerator or an air-conditioner, using a vapor compression refrigerating cycle.
These years, due to a tendency of increase demands of prevention of earth warming and reduction in running cost, energy saving as to refrigerators and air-conditioners which causes energy consumption in a large part in tenants and buildings has been promoted. In order to enhance the efficiency of a refrigerating machine such as an air-conditioner or a refrigerator and to lower the costs thereof, as disclosed in JP-A-2001-227778, it has been known to use a built-in magnet synchronous motor for driving a compressor, having an armature incorporating a squirrel cage conductor and a permanent magnet so that the motor serves not only as an induction motor but also a synchronous motor.
In the above-mentioned conventional technology, of a plurality of compressors used in a refrigerating machine, the one compressor which is a variable speed compressor driven by a built-in magnet synchronous motor, is adapted to be subjected to an inverter drive, but the other one or more compressors which are constant speed compressors are driven by a commercial power source. However, although the compressor subjected to an inverter drive is driven with a relatively high degree of efficiency in the above-mentioned configuration, it has been not yet known in detail how to enhance the overall efficiency of the refrigerating machine.
In the case of synchronous operation of the built-in magnet synchronous motor, overload operation causes the built-in magnet synchronous motor to produce an insufficient torque which deteriorates the synchronous operation so that the armature stalls, result in running of abnormal current therethrough, and accordingly, there would cause a risk of occurrence of a dielectric breakdown of the armature windings.
An object of the present invention is to provide a refrigerating machine using a plurality of compressor and having a comparatively enhanced degree of overall efficiency.
Further, another object of the present invention is to provide a refrigerating machine using a plurality of compressors, which has a degree of reliability that is comparatively enhanced.
To the end, according to the present invention, there is provided a refrigerating machine using a plurality of compressors driven by motors each of which comprises an armature including an iron core having a squirrel cage conductor and a permanent magnet which is magnetized so as to allow the motor to serve as a synchronous motor, and a compressor drive circuit for selectively driving the motors at a power source frequency by a commercial power and at a variable frequency by an inverter.
Further, according to the present invention, there is provided a refrigerating machine comprising a plurality of compressors driven by motors each including an armature having an iron core incorporating a permanent magnet, at least one of the compressors is driven at a variable speed by an inverter, and the other compressors are driven by motors each including an armature incorporating a squirrel cage conductor in addition to the permanent magnet.
Further, according to the present invention, there is provided a refrigerating machine including a plurality of compressors driven by motors each having an armature with an iron core incorporating a squirrel cage conductor and a permanent magnet, and the respective motors can be driven at a power source frequency by a commercial power source and also at a variable frequency by an inverter.
Further, in the refrigerating machine having the above-mentioned configuration, it is desirable to use a scroll compressor as the above-mentioned compressor.
Further, in the refrigerating machine having the above-mentioned configuration, it is preferable to wind armature windings concentrically in a stator in the motor.
Further, in the above-mentioned compressor having the above-mentioned configuration, it is preferable to use a scroll compressor as the above-mentioned compressor, and to wind armature windings concentrically in a stator of the motor.
Further, in the above-mentioned machine having the above-mentioned configuration, when it is determined that the inverter fails, it is preferable to drive at least one of the plurality of compressors by a commercial power source.
Further, in the refrigerating machine having the above-mentioned configuration, every one of the plurality of compressors is driven by a motor including an armature having an iron core which incorporates a squirrel cage conductor and a permanent magnet that is magnetized so as to allow the motor to serve as a synchronous motor.
In the refrigerating machine having the above-mentioned configuration, the plurality of compressors have a uniform type.
Further, in the refrigerating machine having the above-mentioned configuration, there is provided a pressure detecting device on the discharge side of the compressor which is therefore driven in accordance with a value detected by the pressure detecting device.
Present invention will be hereinbelow detailed in the form of preferred embodiments with reference to the accompanying drawing in which.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.